RRM1 and head and neck squamous cell carcinoma: The FA-HNSCC cell lines were all sensitive to gemcitabine treatment (Fig. 2c), in line with the RNA interference data of RRM1 and RRM2. Notably, both the FA- and non-FA fibroblasts were relatively resistant to gemcitabine (Fig. 2d), excluding a synthetic lethal interaction between RNR inhibition and a defective FA/BRCA pathway.